Conventionally, there is an autofocus control apparatus that performs focus control using image signals acquired by an image sensing element that photoelectrically converts an optical image of an object formed by an image sensing optical system.
As such an autofocus control apparatus, there has been proposed an autofocus control apparatus that uses both an autofocus system employing contrast detection and an autofocus system employing infrared ray detection, and performs a focusing operation which uses the autofocus system employing contrast detection at the time of a normal image sensing operation and, on the other hand, switches to the autofocus system employing infrared ray detection only under an image sensing environment in which the focusing operation according to the autofocus system employing contrast detection is difficult, to thereby perform a distance measurement operation and an autofocus operation with respect to a desired subject. With such an apparatus, appropriate autofocus can be performed regardless of brightness of a subject (e.g., see Japanese Patent Laid-Open No. 5-119250).
In addition, as another autofocus control apparatus, there has been proposed an autofocus control apparatus that uses both an autofocus system employing contrast detection, which photoelectrically converts an optical image of an object to generate image signals and detects a predetermined high-frequency component from the generated image signals to thereby perform focusing, and an autofocus system using a light-emitting unit (LED) irradiating an infrared ray and infrared ray detection, which receives reflected light from an object to detect an output signal corresponding to a distance to the object, and selects at least one of the autofocus system employing contrast detection and the autofocus system employing infrared ray detection on the basis of an output from a temperature detection device which detects environment temperature to thereby perform an autofocus operation. According to this autofocus control apparatus, appropriate autofocus can be performed regardless of a change in environment temperature when the apparatus is in use (e.g., see Japanese Patent Laid-Open No. 2000-111792).
However, in the above-described conventional examples, at least one of the autofocus system employing contrast detection and the autofocus system employing infrared ray detection is selected according to brightness of a subject or environment temperature when an apparatus is in use to perform an autofocus operation.
Consequently, there is a disadvantage that it is necessary to separately provide an autofocus device employing infrared ray detection in addition to an image sensing device for photoelectrically converting an object image formed by an image sensing optical system, which leads to an increase in cost. In addition, in the case in which one of the autofocus systems is selected to perform an autofocus operation, there is a disadvantage that a high-speed and high-precision autofocus operation cannot be performed.